Sound recording and reproducing apparatus



G. L. DIMMICK scum) RECORDING AND REPRODUCING APPARATUS Se t. 21, 1937.

Filed May 9, 1952 2 Sheets-Sheet 1 Edi,

I m MY RM E mfl lm m m M 6 Sept. 21, 1937. s. L. DIMMICK SOUND RECORDING AND REPRODUCING APPARATUS Filed May 9, 1932 2 Sheets-Sheet 2 INVENTOR G. L. DiMMlCK BY M 4 I MW ATTORNEY Patented Sept. 21, 1937 UNITED STATES- PATENT OFFICE SOUND RECORDING AND REPRODUOING APPARATUS of Delaware Application May 9, 1932, Serial No. 610,302

8 Claims.

This invention relates to sound recording and reproducing apparatus, and has for its principal object the provision of an improved apparatus and method of operation. whereby the ground or background noise resulting from dust and scratches on a photographic film record is eliminated, the distortion usually resulting from the imperfect resolving power of such a film is avoided, and the high frequency response from the film during reproduction is greatly improved.

A further object is the provision of an improved sound record on which the positive and negative undulations are recorded on separate tracks spaced from one another so as to permit their images to be focused separately on different light responsive elements.

A further object is the provision of a sound record which may be utilized in connection with an alternating current exciter lamp without the production of an alternating current hum or other objectionable noise.

In some respects, this improved record is similar to the push-pull types of record disclosed by United States Patent Nos. 364,472, 1,213,616, 1,291,702 and 1,338,719. It differs from these different types of record in that the records of the oppositely directed undulations are spaced from one another. Depending on the type of recorder utilized, they may appear either along the opposite edges of the strip usually reserved for the sound track or along parallel sections intermediate the edges of this strip.

From a practical viewpoint, the spacing apart of the positive and negative undulation records has several important advantages not heretofore realized. Due to the separation of the positive and negative component records, the fogging between peaks at high frequency is avoided, ground noise is eliminated due to the fact that the record is opaque at zero modulation, the tendency Figs. 4 and 5 are explanatory diagrams relating to another type of record.

Figs. 7 and 8 are explanatory diagrams relating to a further type of record.

Fig. 3 is a diagrammatic showing of a recording apparatus for producing the type of record illustrated by Fig. 5,

Fig. 6 is a diagrammatic showing of a recording apparatus for producing the type of record illustrated by Fig. 8, and

Fig. 9 is a diagrammatic showing of an apparatus for reproducing sound from the records illustrated by Figs. 5 and 8.

Fig. 1 illustrates a light silt member In a light slit ll. If a light beam I2 is vibrated from its illustrated position as indicated by the arrow a variable area record similar to that illustrated by Fig. 2 is produced. This record includes a dark portion I3 and a clear portion 14. In reproducing sound from this record it has been found that scratches and dust on the clear part M produce a disagreeable background noise, and that due to imperfections in the resolving power of the photographic film usually used for such records the valleys between the peaks are likely to be fogged, especially at high frequencies.

A type of record which avoids these diiiiculties is illustrated by Fig. 5. On this record the oppositely directed undulations or the positive and negative components It? and it appear at the opposite edges of the sound track W. This record is produced by transverse vibration of a light beam I8 longitudinally of a slit l9. It will be observed that the light beam I8 is biased to a position where the slit is completely covered by an opaque central portion 20 at zero modulation. Under these conditions, the final positive record is completely black when there is no sound and the possibility of ground noise is precluded.

It is desirable, under some conditons, that the 'postive and negative component records be not only spaced from one another, but also spaced from the edges of the sound track. A record of this type is illustrated by Fig. 8. One way of producing this record is by means of a pair of tri-- angular light beams 2| and 22 which are vibrated transversely of the slit I9.

As indicated by Fig. 3, the type of record illustrated by Fig. 5 may be produced by interposing in the optical system of a recorder a target 23 provided with an aperture 24 and a rectangular member 25 arranged to shade the aperture 24 at zero modulation. The recording apparatus includes a light source 26 from which light is proiected through a lens 21 to a mirror 28 from which it is reflected through a lens 23 to a mirror 30. which'is vibrated in accordance with the imflpulses to be recorded. It willbe noted that the 7 image appearing on the reflector 23 lain the form of a dark central square surrounded by an illuminated angularly shaped area. The arrangement is such that the central dark area is refiectedon to the aperture :4 of the target 2:

- light stop 34 provided with triangular openings 35 and 36 and a light slit member 31. light from anexciter lamp 38 is transmitted through a lens 39, the stop 34 and a lens 40 to a vibratable mirror 4| arranged to move about an axis perpendicular to the direction of motion of the film. Light is reflected from the mirror 4! through a lens 42, the slit of the member 31, and an objective 43 to a record 44. As will be readily understood, no light is applied to the record 44' at zero modulation or when no current is supplied to the coil upon which the mirror 4| is supported. Upon vibration of the mirror 4|, however, the triangular light beams reflected from it are moved transversely of the slit and a record of the type illustrated by Fig. 8 is produced. This record has the advantage that the positive and negative component records are spaced from the edges of the sound track and are less likely to be worn or scratched.

Fig. 9 illustrates an apparatus which may be utilized to reproduce sound either from the type of record illustrated by Fig. 5 or that illustrated by Fig. 8. It includes an exciter lamp 45 which maybe of the alternating current type and from which light is transmitted to a light responsive element 46 through an optical system 41, the record 44, a spherical lens 48 and a pair of lenses 49 and '50 which are provided for focusing the separate images of the positive and negative component records. The photoelectric or light responsive device 46 includes an anode BI and a pair of cathodes 52 and 53 which are connected to the end terminals of a transformer winding 54. The anode 5| is connected to an intermediate terminal of this winding through a battery 55. Inductively associated with the winding 54 is a winding 56 through which current may be supplied to a loudspeaker amplifier or the like.

As will be readily understood by those skilled in the art, the optical system of 41 functions to produce a narrow line of light on the film 44 and the images of the positive and negative component records are respectively focused by the lenses 49 and 50 on the cathodes 52 and 53. Current is transmitted through the winding 54 in one direction when the cathode 52 is illuminated and, through this winding, in the opposite direction when the cathode 53 is illuminated. Since the amplifying part of the apparatus forms no part of this invention, it has been omitted in order to simplify the drawings.

aooasss Having thus claimis: Q 7

1. The combination of an alternating current light source, a record whereon the positive and negative components of sound are recorded on separateareas, means for focusing light from said source-on said areas, a pair of light responsive elements connected in push-pull and lodescribed my invention, what I sound comprising means for moving a film past a recording point, and -means for independently producing records corresponding respectively to the positive and negative components of a sound wave, each record being symmetrical about its fi and'the axes being spaced apart upon the, 4. A sound record comprising a plurality of spaced soundtracks symmetrically arranged in relation to the axis of said record, the said soundtracks respectively including opposite and symmetrical halves only of each sound wave, and each soundtrack being symmetrical about its own axis.

5. A sound record comprising a plurality of soundtracks symmetrically spaced in relation to the axis of said record, said soundtracks including respectively symmetrically opposite halves of each sound wave and being symmetrical about its own axis.

6. A sound record comprising a plurality of complementary soundtracks symmetrically spaced in relation to the axis oi said record, said soundtracks respectively including symmetrically opposite halves of each sound wave and each half wave soundtrack being symmetrical about its own 7. A sound record comprising a plurality of complementary soundtracks symmetrically spaced in relation to the axis of said record, said soundtracks respectively including only symmetrically opposite halves of each sound wave and each half wave soundtrack being symmetrical about its own axis.

8. A sound record comprising a plurality of complementary soundtracks symmetrically spaced in relation to the axis of said record, said soundtracks respectively including only symmetrically opposite halves of each sound wave and each half wave sound track being symmetrical about its own axis, and neither soundtrack including a sound recording at such points as correspond to a sound recording on the other track.

GLENN L. DIMMICK. 

